The present disclosure relates to a battery pack capable of being used for the power source of an electric power-assisted bicycle, an electric motorcycle or the like, and an electric vehicle which uses the battery pack.
An electric power-assisted bicycle is a bicycle which performs input aids by an electric motor. An electric motorcycle can travel by using only the electric motor. A battery pack is used as the power source of the electric motor. For example, a lithium-ion secondary battery which uses doped or undoped lithium ion is used as the battery pack. In a case of the electric power-assisted bicycle, the electric motor is attached to the base or the like of a pedal.
When a battery pack is charged, the battery pack is removed first from the bicycle, and the battery pack is charged using the power source of a household and a dedicated battery charger. Therefore, in a case of the battery pack of an electric power-assisted bicycle, an operation to remove, transport, and attach the battery pack is often performed. In addition, in a case of the electric power-assisted bicycle, a necessary battery capacity is comparatively large, and thus the battery pack thereof becomes heavy. For example, there is a case in which the battery pack is equal to or greater than 3 kg. Therefore, if the battery pack is dropped when an operation to replace the battery pack is performed, a large impact is applied to the battery pack. If external impact is propagated to battery cells in the battery pack, the external impact causes liquid to leak out of the battery cells and causes the battery cells to be transformed.
Therefore, it is desirable to improve the impact resistance of the battery pack and to prevent external impact from being propagated to the battery cells. PTL 1 below discloses a technology in which a buffer material is inserted to the inside of a battery pack and impact applied to the battery pack is absorbed by the buffer material.